TOPTICA‘s CTL is the ideal laser
for demanding tasks that require
wide wavelength tuning without any
mode-hopping. It guarantees completely mode-hop-free scans across
a range of up to 110 nm with highest
resolution.

Combined with its narrow linewidth,
high power and full digital control, the
CTL sets new standards for tunable
lasers. This is the perfect tool to
expand your horizon!

Continuous Tuning TOPTICA

Up to 110 nm mode-hop-free
wavelength tuning
Scan resolution down to 5 kHz
Available at 950, 1050, 1320,

1470,1500 and 1550 nmUp to 80 m W output powera) b) c)

A
B
C

CGH data in thehighlighted regionASI data in thesame region

Further close-ups indicate some sys-
tematic mid-spatial frequency artifacts
in the CGH measurement. CGHs typically have to manage multiple diffraction
orders in their design, and these can introduce artifacts into the measurement.

In this example, several locations on the
part exhibit such artifacts. Local hot
spots from higher diffraction orders are
visible in position A, and show up as localized bumps with rings in the phase
map (see Fig. 4). Stronger artifacts are
present at location B that cause phase
unwrapping and data dropout, forcing
those locations to
be masked entirely. Location C exhibits another type
of artifact where
spurious fringes
introduce ripples
into the measure-
ment. All of these
artifacts are absent
in the stitched ASI
measurement.

Lateraldistortion

Lateral registration
and local magnification is another consideration
with interferometry.

Spheres, aspheres,and freeforms can-not be projectedonto a plane with-out some form ofdistortion (simi-lar to maps of theearth). For qualityassessment, distortion is not of great con-cern, as it does not materially alter metricssuch as peak-to-valley or rms. However,for deterministic correction of a surface,distortion can be quite important sinceit is important to know where a featureis to correct it.

The typical interferometer mapping
assumption is a direct projection to the
equatorial plane (analogous to looking
straight down at the part). Aspheric null
tests, however, often deviate from this assumption, and this example CGH test is
no exception.